This stately mansion, built in 1787 by America's first Secretary of the Navy, is rumored to be one of the most haunted buildings in Washington, DC.

The walls of the iconic dome are hollow and have a secret stairway.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

People escaping slavery may have hidden inside a corpse vault.

A wondrous old library overlooking the nation's capital.

This grand gothic brewery has been pumping out suds for over a hundred years.

The oldest continuously operating fish market in the United States.

Home to items never before seen by the public.

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

The United States Capitol's former columns still stand.

This medieval sanctuary's tree-framed door looks like a portal to a mythical realm.

This centuries-old hotel hides a network of secret cellars and passages once used by smugglers.

A labyrinthine underworld of tunnels and caverns hides beneath the city.

One of the few standing Roman lighthouses and a labyrinth of tunnels are a couple of the secrets at this historic castle.

Under a church hides a forgotten 13th-century ossuary containing the remains of around 2,500 people.

The granddaddy of English geoglyphs dates back to the late Bronze Age.

Cliffs full of fossils at the portal to England's Jurassic Coast.

These stark white cliffs were spat up by the sea and are slowly being retaken by it.

The ritual has been performed uninterrupted for nearly 700 years.

England's most notorious suicide spot.

A house of bones — but nobody is quite sure to whom they belong.

The ruins of an 11th-century Norman castle with a rare, perfectly circular shape.

Follow the original medieval paths that wind through this intriguing section of the city.

It is said the legendary wizard once lived in this sea cave beneath Tintagel Castle.